1. Field of the Invention
The invention relates to a control apparatus for a vehicle, and a method of controlling a vehicle. More specifically, the invention relates to a technology in which torque output from a power source is boosted during a toque phase when an automatic transmission upshifts.
2. Description of the Related Art
When an automatic transmission upshifts, a driving force decreases during a torque phase, and then the driving force increases and a shock occurs when the torque phase ends and an inertia phase starts. To suppress the shock when the automatic transmission shifts, the technology in which the torque is boosted during the torque phase is proposed.
Japanese Patent Application Publication No. 2001-248466 (JP-A-2001-248466) describes an upshift shock reduction apparatus for an automatic transmission for a vehicle that includes a power train that includes a power source and the automatic transmission. When the automatic transmission upshifts, the upshift shock reduction apparatus boosts torque output from the power source, and then decreases the torque during the torque phase, thereby reducing a shock due to a decrease in the torque during the torque phase.
The upshift shock reduction apparatus described in the patent publication changes a timing at which the torque output from the power source starts to be decreased after the torque is boosted, according to the load of the power source so that the torque reliably starts to be decreased before the start of the inertia phase. Thus, although the start of the inertia phase chances according to the load of the power source, the torque reliably starts to be decreased before the start of the inertia phase. Therefore, the torque output from the power source is not maintained at a large value until the inertia phase starts. As a result, it is possible to avoid a problem that a shock occurs in an initial stage during the start of the inertia phase, or a problem that the inertia phase does not start until the end of the decrease in the torque.
The progress of the gear shift depends on the relation between torque input to the automatic transmission and transmission torque of a friction engagement element to be engaged (engagement pressure for the friction engagement element). When the transmission torque exceeds a value set in accordance with the input torque, the inertia phase starts. It is important to start the inertia phase by appropriately controlling the relation between the input torque and the transmission torque. However, the upshift shock reduction apparatus described in Japanese Patent Application Publication No. 2001-248466 decreases the increased engine torque in a stepwise manner during the torque phase. Therefore, it is difficult to appropriately control the relation between the input torque and the transmission torque. As a result, a shock may occur during the gear shift.